A wear-resistant housing for a screw extrusion device is disclosed in German Patent Specification No. 24 26 732 (U.S. Pat. No. 4,036,540). In such prior specification, there is disclosed a hollow cylindrical housing within which at least one screw rotates. The internal surface of the housing has a plurality of recesses uniformly distributed around its periphery but spaced from one another. Wedge-shaped wear-resistant insert members are inserted into these recesses.
The milling of individual recesses in the internal wall of the housing is a precision operation and is time-consuming. Moreover, the precision production of the insert members to be fitted into the milled recesses is equally time-consuming. To produce the individual wear-resistant insert members sufficiently accurately to ensure that they are firmly retained in position, very expensive machine tools are required. The machine tools which are used must have a hardness which is greater than that of the wear-resistant parts and, in consequence, they are extremely cost-intensive.